Question: Solve for $r$ : $8 = 24 + r$
Solution: Subtract $24$ from both sides: $ \begin{eqnarray} \\ \hphantom{8 {- 24}} &\hphantom{=}& \hphantom{r} \\ 8 &=& 24 + r \\ \\ {-24} && {-24} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 8 {- 24} &=& r \\ \end{eqnarray} $ Simplify. $ r = -16$